News tagged with microwave radiation

(PhysOrg.com) -- The last tests of the Ariane 5 rocket system have been finished and ESA's Planck satellite is sitting ready for launch at the Guiana Space Centre in Kourou. Together with ESA's space telescope Herschel, Planck ...

(Phys.org)—The NASA/ESA Hubble Space Telescope – with a little help from an amateur astronomer – has produced one of the best views yet of nearby spiral galaxy Messier 106. Located a little over 20 million light-years ...

(Phys.org) -- A team of researchers at Boston University (BU), Massachusetts Institute of Technology (MIT) and a number of other institutions recently observed that certain materials undergo an insulator-to-metal transition ...

A metal object can be made invisible with the help of ordinary plastic, Pekka Alitalo and Constantinos Valagiannopoulos, researchers from the School of Electrical Engineering, have shown in their study.

(Phys.org) —SLAC scientists have found a new way to produce bright pulses of light from accelerated electrons that could shrink "light source" technology used around the world since the 1970s to examine details of atoms ...

The universe was created 13.7 billion years ago in a blaze of light: the big bang. Roughly 380,000 years later, after matter (mostly hydrogen) had cooled enough for neutral atoms to form, light was able to traverse space ...

(PhysOrg.com) --Almost 400,000 years after the universe was created in the big bang, matter cooled sufficiently for neutral atoms to form, thereby allowing the pervasive light to propagate almost completely unhindered.

Microwave

Microwaves are electromagnetic waves with wavelengths ranging from 1 m down to 1 mm, or equivalently, with frequencies between 0.3 GHz and 300 GHz.

Apparatus and techniques may be described qualitatively as "microwave" when the wavelengths of signals are roughly the same as the dimensions of the equipment, so that lumped-element circuit theory is inaccurate. As a consequence, practical microwave technique tends to move away from the discrete resistors, capacitors, and inductors used with lower frequency radio waves. Instead, distributed circuit elements and transmission-line theory are more useful methods for design and analysis. Open-wire and coaxial transmission lines give way to waveguides, and lumped-element tuned circuits are replaced by cavity resonators or resonant lines. Effects of reflection, polarization, scattering, diffraction and atmospheric absorption usually associated with visible light are of practical significance in the study of microwave propagation. The same equations of electromagnetic theory apply at all frequencies.

While the name may suggest a micrometer wavelength, it is better understood as indicating wavelengths very much smaller than those used in radio broadcasting. The boundaries between far infrared light, terahertz radiation, microwaves, and ultra-high-frequency radio waves are fairly arbitrary and are used variously between different fields of study. The term microwave generally refers to "alternating current signals with frequencies between 0.3 GHz (3×108 Hz) and 300 GHz (3×1011 Hz)." Both IEC standard 60050 and IEEE standard 100 define "microwave" frequencies starting at 1 GHz (30 cm wavelength).

Electromagnetic waves longer (lower frequency) than microwaves are called "radio waves". Electromagnetic radiation with shorter wavelengths may be called "millimeter waves", terahertz radiation or even T-rays. Definitions differ for millimeter wave band, which the IEEE defines as 110 GHz to 300 GHz.